Long Term Evolution (LTE) of the Universal Mobile Telecommunication System (UMTS) technology is a major new technology research and development project initiated by the 3rd Generation Partnership Project (3GPP) in recent years. This technology has been provided with some features of the 4th Generation communication technology and thus can also be regarded as a “quasi-4G technology”. It improves and enhances the 3G air-interface access technology, adopts Orthogonal Frequency Division Multiplexing (OFDM) and Multi-Input Multi-Output (MIMO) as key technologies of its wireless network evolvement, and better addresses the problem of intra-cell interference and achieves a higher network capacity, a higher peak rate and a wider network coverage as compared with the CDMA technology. However this comes with the cost of a possibly more serious problem of Inter-cell Interference (ICI) arising in the OFDM system than the CDMA system.
The technology of Coordinated Multiple-Point (CoMP) as one of key technologies of Long Term Evolution-Advanced (LTE-A) can address effectively the ICI problem and improve significantly a cell throughput and an edge user rate. Particularly in a Joint Transmission (JT) solution in CoMP as illustrated in FIG. 1, transmission data is shared between cooperating cells, and the entire cluster of cooperating cells serves concurrently one or more User Equipments (UEs). This can eliminate interference between the respective cells but also convert the interference into a useful signal to thereby improve greatly the performance of a cell edge user equipment. For the purpose of CoMP transmission, a Base Station (BS) needs to obtain channel quality conditions between all the users and the base station in a cooperation area. For example, in the LTE system, downlink channel information is fed from a user equipment back to the base station over an uplink channel. The feedback information generally consists of two parts which are a Precoding Matrix Indicator (PMI) (reflecting channel direction information) and a Channel Quality Indicator (CQI) (reflecting channel quality information). The base station determines from the PMI a precoding scheme for data to be transmitted and determines from the CQI a modulation scheme for the data to be transmitted.
In the LTE R10, the CQI fed back from the user equipment is designed for per-cell MIMO without regard to the CoMP joint transmission scenario. It is thus desirable to design a new downlink channel information feedback solution for the CoMP joint transmission scenario.
Moreover it has not been definitely specified in the LTE R10 as to how to determine a transmission set composed of cells participating in CoMP joint transmission to the user equipment. It is thus desirable to develop a solution to determination of a transmission set for a user equipment.